From: Patrick Hurley <phurley@...>
Date: 2005-12-22T19:05:44+09:00
Subject: Re: When are attr_reader type methods called?

On 12/22/05, Vivek <krishna.vivek@gmail.com> wrote:
> class X
>   @ivar = 1
>   def self.call_this
>      puts "call this"
>      @var = 1
>   end
> end
> class A <X
>   call_this
>   def some_method(arg)
>     puts arg
>   end
> end
> puts X.instance_eval { @var}
> puts X.instance_eval { @ivar}
>
>
> I have  a statement like @var = 1 inside a class method 'call_this'
> ,but @var is an instance variable,so who come I dont get  an error?

You are asking the right questions, if you are feeling adventurous do a quick:
ri Class

X is also an Object -- the variable @ivar is an instance variable in
that class. Similarly the instance variable @var you create in the
call_this method, becomes an instance variable in the class A. Try
this:

puts A.instance_eval { @var }    # -> 1

Also note that if you:

X.call_this
puts X.instance_eval { @var }    # -> 1

> And second
> I read the documentation of instance_eval at The practical programmer
> site..which says.
>
> instance_eval    obj.instance_eval(aString  [, file  [  line  ]  ] ) ->
> anObject
>
> But here and in Ross' examples we call it on a class ? Is the
> documentation incorrect or am i missing something.

You were (because I know you got it from my pitiful explanation :-)
were missing that a Class is an Object.

Good Luck and keep at it
pth